Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$33.41	10.296%	$36.8499	$36.85	$36.85	$36.80
Purchase #2	$186.46	5.131%	$196.0273	$196.03	$196.05	$196.00
Purchase #3	$106.66	5.741%	$112.7834	$112.78	$112.80	$112.80
Purchase #4	$55.93	4.453%	$58.4206	$58.42	$58.40	$58.40
Purchase #5	$16.30	6.725%	$17.3962	$17.40	$17.40	$17.40
Purchase #6	$144.37	5.500%	$152.3104	$152.31	$152.30	$152.30
Purchase #7	$231.69	8.689%	$251.8215	$251.82	$251.80	$251.80
7 purchase totals =	$774.82		$825.6093	$825.61	$825.60	$825.50